1. Field of the Invention
The present invention relates to a supercooling control expansion valve having a pressure detecting function for use in a refrigerating cycle. More particularly, the present invention relates to a supercooling control expansion valve unit having a pressure detecting function, in which a pressure detector is integrally joined to a supercooling control expansion valve.
2. Description of the Related Art
Thermostatic expansion valves are widely employed as expansion valves for use in refrigerating cycles. Supercooling control expansion valves are also used in refrigerating cycles as expansion valves that control the flow rate of a refrigerant entering an evaporator by detecting the degree of supercooling of the high-pressure refrigerant before it is sent into the evaporator. It is known that the use of a supercooling control expansion valve allows the whole system to be constructed in a compact form. A supercooling control expansion valve is incorporated in a refrigerating cycle comprising a compressor, a condenser for condensing a high-pressure refrigerant, a pressure-reducing device for reducing the pressure of the condensed refrigerant, an evaporator for evaporating the refrigerant after the pressure reduction, an accumulator, and so forth. The supercooling control expansion valve is placed upstream of the evaporator.
Meanwhile, the refrigerating cycle is provided with a sensor for detecting the pressure of the refrigerant and outputting the quantity of state thereof in the form of an electric signal to control the function of the refrigerating cycle normally. Examples of the detecting sensor include a pressure sensor and a pressure switch having electric contacts. Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 11-351990 proposes a pressure sensor adopting an absolute pressure method or a sealed gauge pressure method as a detecting sensor usable in a refrigerating cycle.
Thus, various devices have been developed and proposed as individual units. However, these devices are incorporated into the above-described refrigerating cycle as discrete component parts in the present state of the art. The assembly of the discrete component parts needs an unfavorably large number of man-hours for piping work and so forth. When these component parts are used in the refrigerating cycle of air-conditioning systems installed in motor vehicles or the like in particular, the component parts are generally manufactured by mass production. Therefore, the number of man-hours needed for the assembly inevitably increases in proportion to the production output, and the parts count (i.e. the number of constituent parts) also increases. Accordingly, there are demands that the assembly man-hours and the parts count should be minimized.
To meet these demands, Japanese Utility Model Application Unexamined Publication (KOKAI) No. Sho 55-144268 proposes a pressure switch-incorporating expansion valve unit comprising a pressure switch and an expansion valve combined together into one unit. The pressure switch-incorporating expansion valve unit is expected to save piping and to simplify the assembly operation. However, a diaphragm for driving the valve element of the pressure switch-incorporating expansion valve unit responds to the evaporator outlet-side refrigerant supplied thereinto through a pipe. In addition, the diaphragm and the casing of a pressure switch for detecting the pressure of the evaporator outlet-side refrigerant are placed away from each other.
Therefore, the detection of the refrigerant pressure is performed separately at two positions, i.e. at the position of the pressure switch and at the position of the diaphragm for driving the valve element. Thus, the temperature response characteristics of the two pressure detections do not match to each other because the detections are made at different positions. Accordingly, the temperature response of the system is not very fast.
The present invention has been developed with the above-described technical background to attain the following objects.
An object of the present invention is to provide an expansion valve unit having a pressure detecting function that is made compact by integrally incorporating a pressure detector into a supercooling control expansion valve.
Another object of the present invention is to provide an expansion valve unit having a pressure detecting function that is reduced in the number of man-hours needed for incorporation into a refrigerating cycle by combining together a supercooling control expansion valve and a pressure detector into one unit.
A further object of the present invention is to provide an expansion valve unit having a pressure detecting function that is reduced in the parts count to minimize the production cost.
A further object of the present invention is to provide an expansion valve unit having a pressure detecting function that is improved in the response for pressure detection of the expansion valve.
A further object of the present invention is to provide an expansion valve unit having a pressure detecting function in which the response characteristics of the refrigerant pressure detector and the response characteristics for pressure detection of the expansion valve are matched to each other.
According to a first aspect of the present invention, there is provided an expansion valve unit having a pressure detecting function. The expansion valve unit includes a supercooling control expansion valve disposed in a flow path of a refrigerant sent into an evaporator of a refrigeration system constituting a refrigerating cycle to control the flow rate of the refrigerant. A pressure detector is provided at one end of the supercooling control expansion valve to detect the pressure of the refrigerant sent thereto through a refrigerant passage in the supercooling control expansion valve. The pressure detector is integrally joined to the supercooling control expansion valve by a joining means. A hermetic seal member is disposed near the joint between the supercooling control expansion valve and the pressure detector to prevent leakage of the refrigerant. A hermetically sealed space is formed in a block constituting the base body of the supercooling control expansion valve. The hermetically sealed space surrounds a flow rate control member incorporated in the supercooling control expansion valve and communicates with the refrigerant passage.
According to a second aspect of the present invention, there is provided an expansion valve unit having a pressure detecting function. The expansion valve unit includes a supercooling control expansion valve disposed in a flow path of a refrigerant sent into an evaporator of a refrigeration system constituting a refrigerating cycle to control the flow rate of the refrigerant. A pressure detector is provided at one end of the supercooling control expansion valve to detect the pressure of the refrigerant sent thereto through a refrigerant passage in the supercooling control expansion valve. The pressure detector is integrally joined to the supercooling control expansion valve by a joining means. A hermetic seal member is disposed near the joint between the supercooling control expansion valve and the pressure detector to prevent leakage of the refrigerant. A power element chamber is provided in a block constituting the base body of the supercooling control expansion valve. The power element chamber is defined by a diaphragm and has a refrigerant sealed therein to control the degree of opening of a valve element of the supercooling control expansion valve. A first space is formed adjacently to the power element chamber. The first space communicates with the refrigerant passage. The first space is filled with a high-temperature and high-pressure refrigerant and disposed closer to the pressure detector than the power element chamber. A second space is formed adjacently to the first space on the side thereof closer to the pressure detector. The pressure detector is disposed between the first space and the second space to detect the pressure of the high-temperature and high-pressure refrigerant on the basis of a pressure difference between the first space and the second space.
In the expansion valve unit having a pressure detecting function according to the first or second aspect of the present invention, the hermetic seal member should preferably be an O-ring for sealing the gap between the pressure detector and the block.
In the expansion valve unit having a pressure detecting function according to the first or second aspect of the present invention, the pressure detector should preferably detect the pressure of the refrigerant with a pressure detecting device comprising a semiconductor device.
In the expansion valve unit having a pressure detecting function according to the first or second aspect of the present invention, the pressure detector should preferably detect the pressure of the refrigerant with a contact type pressure switch.
In the expansion valve unit having a pressure detecting function according to the first or second aspect of the present invention, the joining means should preferably be caulking whereby the block is plastically deformed.
In the expansion valve unit having a pressure detecting function according to the first or second aspect of the present invention, the joining means should preferably be thread coupling wherein the pressure detector is fixed to the supercooling control expansion valve by thread engagement.
In the expansion valve unit having a pressure detecting function according to the first or second aspect of the present invention, the thread coupling should preferably be such that the pressure detector is fixed to the block by engagement between a nut having an internal thread and an external thread provided on the outer periphery of the block.
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings.